Published studies indicate that visible wavelength reflectance and fluorescence spectroscopy are each promising techniques for clinically recognizing vulnerable plaque (VP) - a condition prone to rupture and produce arterial thrombosis. Reflectance is already visually accessible in normal angioscopy, and yellow lipid may be seen diffusely through an otherwise white fibrous cap, depending on its thickness, and form a qualitative indication for VP. Progress toward a clinically useful instrument for recognizing VP by quantified spectroscopy requires an arterial, optical-fiber based side-looking probe (SLP). It is a primary goal of the Phase-2 program to accomplish this by building on the Phase-1 tissue-probe-spectroscopy modeling, probe construction techniques developed, and probe - tissue measurements obtained. In the Phase-2 program three SLP designs will be produced and clinically tested in peripheral arteries. The data will be reduced to provide spectrally resolved diffuse reflectance and intrinsic fluorescence. Comparison will be made to results from concurrent Monte Carlo modeling, results from pathology, and results from the measurements of others with respect to characterizing the tissue and recognizing lesions with thin fibrous caps with a significant lipid core - hallmarks of VP. We expect that bringing together the colorimetry information with intrinsic fluorescence will produce results better than either alone. [unreadable] [unreadable]